Field trap for flies

ABSTRACT

A species-selective field trap for flies which comprises a receptacle (1) having a removable lid (4), the receptacle forming a substantially closed chamber(s), when the lid is in place, within which a source of chemical attractant vapor attractive to the selected species of fly and unattractive to most other species of fly is positioned in use. The receptacle having a substantially opaque upper, in use, end (2, 4) which is colored as a visual attractant to the selected species of fly and having one or more small apertures (6) in a side or the lid, thereof adapted to closely accommodate passage of the selected species of fly therethrough. The apertures being the primary and preferably the only means by which the chemical attractant vapor is emitted from the receptacle.

FIELD OF THE INVENTION

The present invention relates to a field trap for selective capture ofone or more species of fly primarily, but not necessarily exclusively,for analysis of fluctuations in the population of the species.

REVIEW OF MOST RELEVANT ART KNOWN TO THE APPLICANT

Field fly traps are widely used in agricultural research and pestmonitoring to assess when and how best to apply insecticide sprays oradopt other measures to protect a field of crop.

The simplest traps for this purpose comprise one or more strips ofbrightly coloured adhesive and, optionally, insecticide-coated paper, ora simple water-containing bowl which is often brightly coloured as anattractant to flies and which may have additional surfactant to assistin drowning flies which land in the water. These traps are howevernon-discriminatory, the choice of attractant colour having little effectin selection of fly species, and give rise to considerable problems insubsequently discriminating between the insect corpses to identify thespecies in question.

A more refined prior art technique involves use of a "lobster pot" trapwhich comprises an open-topped pot substantially sealed, in use, by alid but having a funnel-shaped entrance in the base thereof for entry ofinsects (see FIG. 1). This trap is mounted to a stake which raises itabove ground level in use.

The base of the pot (B) is usually opaque while the main body and upperportions (A) of the pot are transparent. The light within the pot andany suitable chemical attractant which is placed therewithin acts toentice the flies up through the funnel entrance into the pot where it isintended that they will subsequently become disoriented and fail to findtheir way out again.

Whereas the lobster pot design of trap is comparatively more effectivein selecting the desired species of fly than the two afore-mentionedtraps, it is not reliable. This design of pot relies heavily upon theselectively attractive effect of the chemical attractant and is liableto give misleading results due to seasonal and daily variations in theheating of the pot thereby giving rise to fluctuating rates of emissionof the chemical attractant which vaporises far more readily under theglare of the mid-summer sun. A further problem that arises isdesiccation and embrittlement of the fly specimens.

It is a general objective of the present invention to provide a speciesselective fly trap which overcomes the problems of conventional traps.

SUMMARY OF THE INVENTION

A species-selective field trap for flies which comprises a receptaclehaving a removable lid, said receptacle forming a substantially closedchamber, when the lid is in place, within which a source of chemicalattractant vapour attractive to the selected species of fly andunattractive to most other species or fly is positioned in use, andhaving one or more small apertures in a/the side of the lid, in use,thereof adapted to closely accommodate passage of the selected speciesof fly therethrough, said apertures being the primary means by which thechemical attractant vapour is emitted from the receptacle characterisedin that the receptacle has a substantially opaque upper, in use, endextending for a major proportion of the height of the receptacle andwhich is coloured as a visual attractant to the selected species of fly.

Preferably the base, in use, of the receptacle is translucent. A shroudmay be provided extending downwardly, in use, from the base.

Preferably the receptacle is partially filled with an entrapment liquidsuch as, for example, water and preferably also with surfactant. Thisliquid suitably rises within the receptacle to a level just below theaperture(s), thereby ensuring that the flies which enter aresubstantially immediately trapped, and further ensuring greaterconsistency in vapour pressure gradient from within the receptacle tothe exterior.

Where the selected species of fly to be trapped is Delia radicum, thevisual attractant colour is suitably fluorescent yellow, the chemicalattractant is suitably isothio cyanate and the apertures(s) are suitablyapproximately 6 mm in diameter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a "lobster pot" trap of theprior art.

FIG. 2 is a longitudinal sectional view of a field trap according to apreferred embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of the further preferredembodiment of the present invention.

FIG. 4 is a front elevational view of a vial with flip-off lid andseptum, for one embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 2, there is shown a trap which comprises a receptacle1 mounted to an upper end of a stake 2 by means of which the trap may besecurely positioned above ground at any suitable location on a field tobe monitored.

The receptacle 1 comprises a tubular, preferably cylindrical, bodyportion 2, a corresponding tubular base portion 3 which forms a frictionfit within the body portion 2 and a lid portion 4 adapted to engage theupper, in use, end of the body 2 by a friction-fit to substantially sealthe chamber 5 formed within the receptacle 1.

In the illustrated embodiment of FIG. 2, a row of six substantiallysymmetrically spaced circular apertures 6 are provided extending throughthe circumferential wall, or side, of the receptacle body 2. Each of theapertures 6 is of a diameter adapted to closely accommodate passage ofthe selected species of fly to be trapped. Extensive field trials haveshown that for cabbage root fly (Delia radicum) an aperture diameter ofapproximately 6 mm is particularly effective. The diameter of the trapis suitably 65 mm.

The lid 4, body 1 and base portion 3 are entirely formed of fluorescantplastics material (yellow for Delia radicum) with the exception of thefloor 7 of the base portion 3. The colouration renders the lid and sidesof the receptacle 1 substantially opaque and provides a large prominentsurface area of visual attractant to the species of fly to be trapped.This is clearly visible from above for a substantial distance. Theopacity of the upper regions of the receptacle 1 greatly reduces theheating effect of direct sunlight upon the receptacle 1 and therebyreduces not only desiccation of flies trapped but also seasonalvariations in emission of vapour plumes from chemical attractant placedin the chamber 5 of the receptacle 1.

Suitably substantially the whole of the surfaces of the receptacle whichare normally exposed to direct sunlight are opaque. These may includethe whole of the lid and vertical sides of the receptacle.

A source of a chemical attractant which is a host plant chemical orother chemical which is attractive to the target species of fly butunattractive to most other species of fly and may be positivelyrepulsive to most other species of fly, is deposited in small regulardoses upon a retaining member 8 provided extending downwardly from theinner surface of the lid 4. Four doses over a season may be appropriate.For Delia radicum the attractant is suitably allyl isothio cyanate.Plumes of vapour from the source are emitted substantially uniformlyfrom the evenly spaced apertures 6 in the sides of the receptacle bodyportion 2.

The base portion 3 of the receptacle 1 has a shroud 9 extendingdownwardly therefrom which directs reflected light from beneath thereceptacle 1 through the transparent floor 7 into the chamber 5 toattract flies entering the apertures 6 into the base portion 3 of thereceptacle 1.

The base portion 3 is suitably filled with a translucent liquid such aswater having surfactant added thereto to trap and subsequently drown theflies which have entered the chamber 5 via the apertures 6 and eitheraccidentally touched the surface of the liquid or been attracteddownwardly by the source of light.

The illustrated trap incorporates a number of features whichspecifically improve ease and safety of use. These features include theseparability of the body portion 2 of the receptacle 1, the attractantchemical dose retaining member 8 mounted to the lid 4 and the mountingof the base portion 3 to the stake 20.

The supportive stake 20 has a hollow upper region 10 while the baseportion 3 of the receptacle 1 has a leg 11 extending therefrom which maybe slid into the hollow portion 10 of the stake 20. This slidingengagement enables the trap to be lifted and replaced on the stake 2with ease whenever it is desired to empty and inspect the contents ofthe chamber 5. Emptying of the chamber 5 is further facilitated by theseparability of the base portion 3 from the body portion 2, therebyavoiding accidental drainage of water and lots of insect specimensthrough the apertures 6 during emptying.

Provision of the chemical attractant retaining member 8 on the lid 4provides simple access and reduces the need for handling of thechemical.

Referring to FIG. 3, there is shown an improved version of the preferredembodiment of the invention, in which the chemical attractant doseretaining member 8 has cut outs 14 on its innermost end to enable theinner most end to splay to engage a vial 22 containing the chemicalattractant 24. The vial 22 is suitably a glass vial 22 of the type usedfor medicaments and has a flip off lid 22 which, when removed, exposes arubber, preferably natural rubber, septum 28. A chlorobutyl septum isusable but in most circumstances is less efficient, permitting anemission rate of allyl isothio cyanate which is approximately onequarter of that for a natural rubber septum.

The lower portion of the improved trap further differs from theembodiment of FIG. 2 in that the liquid medium is contained within aseparable cup 15 of transparent plastics material. This cup 15 clipsinto an annular base cap 16 into which the lower most edge of thereceptacle body intermediate tubular portion 2 also fits. The base cap16 has a lug 17 projecting therefrom to provide a means of fixing thetrap rigidly to a stake 20 or the like.

Preferred plastics for the construction of the top and bottom caps andthe tubular receptacle body portion 2 comprise dyed ABS, amongst others.The transparent cup 15 is suitably of SAN plastics material.

The illustrated and described trap of the present invention has beenproven to be outstandingly effective in selectively trapping Deliaradicum alone when allyl isothio cyanate attractant is used inconjunction with the aperture size criterion and the appropriatefluorescent yellow colouration of the receptacle 1.

Whereas the present invention has been described above with respect toone preferred embodiment thereof and primarily for one example speciesof fly numerous alternative embodiments are conceivable without exerciseof further inventive thought and falling within the scope of the presentinvention.

What is claimed is:
 1. A species-selective field trap for flies whichcomprises a receptacle having a side wall and a removable lid forcovering an open upper end, and a base, said receptacle forming asubstantially closed chamber, when the lid is in place, within which asource of chemical attractant vapor attractive to the selected speciesof fly and unattractive to most other species of fly is positioned, thereceptacle having a substantially opaque upper end which is colored as avisual attractant to a fly and having one or more apertures in the sidewall thereof to accommodate passage of a fly therethrough, saidapertures being the primary means by which the chemical attractant vaporis emitted from the receptacle, wherein the receptacle is adapted tominimize the heating of the content thereof, the substantially opaqueupper end of the receptacle extending downwardly for the majority of thelength of the receptacle, whereby the receptacle is substantially whollyprotected from direct sunlight entering the receptacle, and said basebeing formed from material permitting greater light passage thanmaterial forming said upper end.
 2. A field trap as claimed in claim 1,wherein the receptacle further includes a translucent base.
 3. A fieldtrap as claimed in claim 1, wherein a shroud is provided extendingdownwardly from the base.
 4. A field trap as claimed in claim 1, whereinthe receptacle is adapted to be partially filled with an entrapmentliquid.
 5. A field trap as claimed in claim 4, wherein the apertures ofthe receptacle are located substantially immediately above the level towhich it is intended that the entrapment liquid will rise in use.
 6. Afield trap as claimed in claim 1, wherein the inner face of the lid ofthe receptacle has a retaining member for the source of chemicalattractant.
 7. A field trap as claimed in claim 6, wherein the retainingmember is adapted to provide a snap-fit mounting for a vial containingthe chemical attractant.
 8. A field trap as claimed in claim 1, whereinthe trap has a main body portion and a base, the base being that portionwithin which the flies collect, and the main body portion and the baseare separable.
 9. A field trap as claimed in claim 1, wherein the trapfurther comprises a vial containing the source of chemical attractantand said vial has a rubber septum.